linux-kernel - Re: [PATCH] ipc/util.c: sysvipc_find_ipc() incorrectly updates position index

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Date:   Thu, 7 May 2020 15:29:37 +0300
From:   Vasily Averin <vvs@...tuozzo.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Waiman Long <longman@...hat.com>, linux-kernel@...r.kernel.org,
        Andreas Schwab <schwab@...e.de>
Subject: Re: [PATCH] ipc/util.c: sysvipc_find_ipc() incorrectly updates
 position index

Dear Andrew,
could you please handle it,
it fixes broken ipcs in last mainline and stable kernels,
and on all its derivatives.

Thank you,
	Vasily Averin

On 5/6/20 6:59 PM, Waiman Long wrote:
> On 5/6/20 2:25 AM, Vasily Averin wrote:
>> new_pos should jump through hole of unused ids,
>> pos can be updated inside "for" cycle.
>>
>> Cc: stable@...r.kernel.org
>> Fixes: 89163f93c6f9 ("ipc/util.c: sysvipc_find_ipc() should increase position index")
>> Signed-off-by: Vasily Averin <vvs@...tuozzo.com>
>> ---
>>   ipc/util.c | 12 ++++++------
>>   1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/ipc/util.c b/ipc/util.c
>> index 7acccfd..cfa0045 100644
>> --- a/ipc/util.c
>> +++ b/ipc/util.c
>> @@ -764,21 +764,21 @@ static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
>>               total++;
>>       }
>>   -    *new_pos = pos + 1;
>> +    ipc = NULL;
>>       if (total >= ids->in_use)
>> -        return NULL;
>> +        goto out;
>>         for (; pos < ipc_mni; pos++) {
>>           ipc = idr_find(&ids->ipcs_idr, pos);
>>           if (ipc != NULL) {
>>               rcu_read_lock();
>>               ipc_lock_object(ipc);
>> -            return ipc;
>> +            break;
>>           }
>>       }
>> -
>> -    /* Out of range - return NULL to terminate iteration */
>> -    return NULL;
>> +out:
>> +    *new_pos = pos + 1;
>> +    return ipc;
>>   }
>>     static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
> 
> Acked-by: Waiman Long <longman@...hat.com>
>